Transcranial Doppler Ultrasound (TCD) MCAv will be measured via the transtemporal window while BAv will be measured through the transforaminal window with 2-MHz (megahertz) transcranial Doppler ultrasound probes. In approximately 30% of individuals the BA cannot be identified; therefore, insonation of the MCA alone will be deemed sufficient to proceed with the study in cases in which BA cannot be located.